Great way is to send a follow up email after a purchase [approx. few days after expected delivery], asking your customer for a review. Make sure to add incentive [10% off next order etc], along the link to leave the review.

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There are lot of SEO forums in which you can ask for a review of your store. E.g. https://forums.digitalpoint.com/, Quora, warriorforum.com etc. Or google 'best forums for SEO'. They often have a category for website review.